CN102832801B - System and method for grouping and pre-charging modular multilevel converter capacitor - Google Patents
System and method for grouping and pre-charging modular multilevel converter capacitor Download PDFInfo
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- CN102832801B CN102832801B CN201210350682.XA CN201210350682A CN102832801B CN 102832801 B CN102832801 B CN 102832801B CN 201210350682 A CN201210350682 A CN 201210350682A CN 102832801 B CN102832801 B CN 102832801B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
- H02M7/4835—Converters with outputs that each can have more than two voltages levels comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/36—Means for starting or stopping converters
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Abstract
The invention relates to a system for grouping and pre-charging modular a multilevel converter capacitor. The system comprises at least one modular multilevel converter MMC; an alternating-current side input end of the modular multilevel converter MMC is connected with a series-connected starting current-limiting resistor Rx, a breaker RBK1 (Remote Breaker) and an alternating-current power supply in turn; or the system comprises two modular multilevel converters MMCs which respectively are a first modular multilevel converter MMC1 and a second modular multilevel converter MMC2. A method for grouping and pre-charging the modular multilevel converter capacitor comprises the following steps of: respectively dividing half-bridge sub-modules of two modular multilevel converters MMCs into two groups and four groups, and carrying out grouping and pre-charging. According to the method for grouping and pre-charging the modular multilevel converter capacitor, the pre-charging of a capacitor is shortened, and the power consumption of the current-limiting resistor is reduced; the charging current direction is unnecessary to be detected, and the capacitor voltage closed-loop control is unnecessary as well; and the implementation is simple, and the control is simple.
Description
Technical field
The present invention relates to a kind of electric capacity grouping pre-charge system and method, particularly relate to the system and method for a kind of Modular multilevel converter electric capacity grouping precharge.
Background technology
Modular multilevel converter (Modular Multilevel Converter, MMC) topology adopts tandem type, modular, directly connect without the need to power device and just can obtain the stepped-up voltage of many level, there is lower dU/dt and lower voltage harmonic content, have broad application prospects in medium/high pressure hicap (as flexible DC power transmission).In the application, system is made up of two three-phase MMC devices usually, this converter topology structure as shown in Figure 1, in figure, every go up brachium pontis mutually and lower brachium pontis has the cascade of N number of submodule (Sub-modular, SM) to form, each submodule SM is half-bridge structure, as shown in Figure 2, submodule DC side parallel has identical capacitor C.
When system is normally run, each submodule capacitor voltage needs to be stabilized near its rated voltage, therefore, before system is normally run, must carry out precharge to submodule SM capacitor C, capacitance voltage is reached or close to its rated voltage.Electric capacity precharge can take charging modes of encouraging oneself, and it also can be adopted to encourage charging modes.
" Proceedings of the CSEE " 2009 the 29th " novel many level VSC submodule capacitance parameter with all press strategy " literary composition (author's fourth champion etc.) of volume the 30th phase 1-6 page publication be referred to kind concise and to the point utilize accessory power supply it encourage charging modes.Choosing the direct voltage source approximating greatly submodule rated voltage, be connected across between MMC converter DC bus both positive and negative polarity, by controlling input and the excision of submodule SM, submodule SM capacitance voltage being risen near rated value.Concrete enforcement is to the Sl cut-off signals of each phase 2N submodule, except submodule to be charged, the S2 of all the other 2N-1 submodule gives triggering signal, direct voltage like this is only carried in submodule electric capacity two ends to be charged, this submodule charges, treat that this submodule capacitor voltage reaches near institute's predetermined value, namely complete the charging of this module.Give this submodule S2 triggering signal subsequently, next submodule S2 to be charged gives cut-off signals simultaneously, and the transfer of charging object, so order is carried out, and can realize the capacitor charging of each phase submodule.But the method needs special auxiliary charging power supply and submodule to control power supply, and each only single submodule drops into charging, and the charging interval of converter doubles.
Publication number is the Chinese patent disclosed " the two-phase modularization multi-level converter starting method without the need to auxiliary DC power supply " of CN101795057A, propose a kind of when without the need to auxiliary DC power supply, the self-excitation charging force method of three-phase modular multilevel inverter, the method AC system line voltage substitutes direct voltage source above, controlled the on off state of each submodule by detection brachium pontis current direction and each submodule capacitor voltage, complete the charging of the submodule of converter.Detailed process is: by current-limiting resistance, alternating voltage is caused converter, cut-off signals is given to switching device S1 on all submodules, triggering signal is given to switching device S2 under all submodules, detect the electric current of each brachium pontis, when electric current is consistent with charging direction, cut-off signals is given to switching device S2 under submodule to be charged, this submodule charges: when electric current is contrary with charging direction, under keeping this submodule, switching device is in off state, this submodule capacitor voltage is kept, so repeatedly, when submodule capacitor voltage reaches specified, switching device S2 under this submodule of triggering and conducting, the charging of this submodule is complete, can transfer to charge to next submodule, repeat above-mentioned steps, until all submodule capacitor voltage of brachium pontis all reaches near rated value, converter submodule electric capacity completes charging.But the method is in converter each brachium pontis/phase charging process, only single submodule drops into charging at every turn, and under same current-limiting resistance, the charging interval of converter doubles; Further, in capacitor charging process, also need to detect charging current direction, control more complicated; In addition, before electric capacity precharge, each submodule externally independently must control power supply, could control switching device, and therefore the method is not suitable for submodule and controls power supply gets energy supply power mode by a capacitance voltage high position.
Publication number is the Chinese patent disclosed " a kind of starting method of modularization multi-level converter flexible direct current power transmission system " of CN102170140A, propose a kind of MMC starting method for flexible DC power transmission, the process employs the starting method that two level converters are conventional, that is, first by current-limiting resistance, uncontrollable rectifier charging is carried out to electric capacity, after capacitance voltage is stable, unlock switch pipe, bypasses current-limiting resistance, and system directly drops into capacitance voltage closed-loop control.Detailed process is divided into three phases: the first stage, first all switching tubes of locking, open current-limiting resistance by-pass switch, uncontrollable rectifier charging is carried out to two current conversion station MMC submodule electric capacity, after capacitance voltage is stable, enter second stage, unlock the switching signal of current conversion station MMC2, and make it enter capacitance voltage closed-loop control, after MMC2 submodule capacitor voltage is stable, enter the phase III, closed current-limiting resistance by-pass switch, unlock the switching signal of current conversion station MMC1, and make it enter capacitance voltage closed-loop control, after two current conversion station submodule capacitor voltage are stable, charging terminates.Although the method is in the first and second stages, owing to there is current-limiting resistance, rush of current is also little, but when the phase III starts, because capacitance voltage is still in (all submodule capacitor voltage sums of each brachium pontis equal AC voltage peak) near lower critical voltage, but after bypassing current-limiting resistance, system directly drops into capacitance voltage closed-loop control, still can produce very large impulse current in practice.
Summary of the invention
Object of the present invention is exactly to solve the problem, and provides a kind of grouping pre-charge system and method for Modular multilevel converter electric capacity, and it has greatly shortens electric capacity precharge time, reduce current-limiting resistance power loss and control simple advantage.
To achieve these goals, the present invention adopts following technical scheme:
A kind of grouping pre-charge system of Modular multilevel converter electric capacity, it comprises at least one Modular multilevel converter MMC, the AC input of described Modular multilevel converter MMC is connected with AC successively and is started current-limiting resistance Rx, AC circuit breaker RBK1 is connected with AC power, described Modular multilevel converter comprises brachium pontis and lower brachium pontis in M phase, described brachium pontis comprises N number of half-bridge submodule SM, N number of half-bridge submodule SM series connection is connected with reactor L, the reactor L of described upper brachium pontis is connected with the reactor L of described lower brachium pontis, its tie point is as the input of described Modular multilevel converter MMC AC one phase, first half-bridge submodule of upper brachium pontis is connected with positive direct-current bus, N number of half-bridge submodule of lower brachium pontis is connected with negative DC bus, described half-bridge submodule comprises power switch tube S 1 and lower power switch tube S 2, upper power switch tube S 1 and lower power switch tube S 2 are in parallel with electric capacity C after connecting.
The grouping pre-charge system of described a kind of Modular multilevel converter electric capacity, it comprises two Modular multilevel converter MMC, be respectively the first Modular multilevel converter MMC1 and the second Modular multilevel converter MMC2, described first Modular multilevel converter MMC1 and the second Modular multilevel converter MMC2 is linked together by DC bus, the AC input of the first Modular multilevel converter MMC1 starts current-limiting resistance Rx with connecting successively, circuit breaker RBK1 is connected with AC power, the AC output of the second Modular multilevel converter MMC2 is connected with circuit breaker RBK2.
Based on a kind of grouping pre-charge method of a kind of Modular multilevel converter electric capacity of grouping pre-charge system of Modular multilevel converter electric capacity, concrete steps are:
Step one: by the half-bridge submodule grouping of respectively going up mutually in Modular multilevel converter MMC in brachium pontis and lower brachium pontis, first half-bridge submodule of upper brachium pontis and lower brachium pontis is divided into first group to N/2 half-bridge submodule, N/2+1 half-bridge submodule to N number of half-bridge submodule in upper brachium pontis and lower brachium pontis is divided into second group, adopts when N is odd number the method rounded up to carry out rounding process;
Step 2: switching tube S1 and S2 of all half-bridge submodules of locking, closed AC power and circuit breaker BRK1, first system enters uncontrollable rectifier pre-charging stage;
Step 3: after capacitor charging makes all half-bridge submodule SM switch controlled power works normal, proceed to grouping pre-charging stage;
Step 4: the lower switching tube S2 conducting triggering second group of half-bridge submodule of described Modular multilevel converter MMC, system is to first of MMC group of half-bridge submodule capacitor charging, when MMC first group of half-bridge submodule capacitor voltage reaches its set point, first group of charging is complete, the now lower switching tube S2 of lock modules multi-level converter MMC second group of half-bridge submodule, the lower switching tube S2 conducting of first group of half-bridge submodule of trigger mode blocking multi-level converter MMC, system is to second of Modular multilevel converter MMC group of half-bridge submodule capacitor charging, when Modular multilevel converter MMC second group of half-bridge submodule capacitor voltage reaches its set point, second group is also charged complete, the lower switching tube S2 of lock modules multi-level converter MMC first group of half-bridge submodule, all half-bridge submodule electric capacity precharge of Modular multilevel converter MMC1 terminates.
In described step 4, can exchange the capacitor charging order of group each in many level blockization MMC.
Based on a kind of grouping pre-charge method of a kind of Modular multilevel converter electric capacity of grouping pre-charge system of Modular multilevel converter electric capacity, concrete steps are:
Step one: by the half-bridge submodule grouping of respectively going up mutually in the first Modular multilevel converter MMC1 in brachium pontis and lower brachium pontis, first half-bridge submodule of upper brachium pontis and lower brachium pontis is divided into first group to N/2 half-bridge submodule, N/2+1 half-bridge submodule to N number of half-bridge submodule in upper brachium pontis and lower brachium pontis is divided into second group;
Step 2: submodules all in the second Modular multilevel converter MMC2 are divided into four groups, first the half-bridge submodule setting each phase of the second Modular multilevel converter MMC2 is first group to N/2 half-bridge submodule, first of brachium pontis half-bridge submodule is respectively descended by second Modular multilevel converter MMC2 to be divided into second group to N/2 half-bridge submodule mutually, N/2+1 half-bridge submodule to N number of half-bridge submodule of the upper brachium pontis of the second Modular multilevel converter MMC2 is divided into the 3rd group, N/2+1 half-bridge submodule to N number of half-bridge submodule of brachium pontis is respectively descended by second Modular multilevel converter MMC2 to be divided into the 4th group mutually,
Step 3: switching tube S1 and S2 of all half-bridge submodules of locking, cut-off breaker BRK2, closed AC power and circuit breaker BRK1, first system enters uncontrollable rectifier pre-charging stage;
Step 4: after capacitor charging makes all submodule SM switch controlled power works normal, proceed to grouping pre-charging stage;
Step 5: the lower switching tube S2 conducting triggering second group of half-bridge submodule of described first Modular multilevel converter MMC1, system is to first of the first Modular multilevel converter MMC1 group of half-bridge submodule capacitor charging, when the first Modular multilevel converter MMC1 first group of half-bridge submodule capacitor voltage reaches its set point, first group of charging of the first Modular multilevel converter MMC1 is complete, the lower switching tube S2 of now locking first Modular multilevel converter MMC1 second group of half-bridge submodule, trigger the lower switching tube S2 conducting of first group of half-bridge submodule of the first Modular multilevel converter MMC1, system is to second of the first Modular multilevel converter MMC1 group of half-bridge submodule capacitor charging, when the first Modular multilevel converter MMC1 second group of half-bridge submodule capacitor voltage reaches its set point, second group of first Modular multilevel converter MMC1 is also charged complete, the lower switching tube S2 of locking first Modular multilevel converter MMC1 first group of half-bridge submodule, so far, all half-bridge submodule electric capacity precharge of the first Modular multilevel converter MMC1 terminates,
Step 6: system proceeds to the grouping pre-charging stage of described second Modular multilevel converter MMC2, if the grouping of MMC2 K represents (K=1,2,3,4), if the initial value of K is 1;
Step 7: the lower switching tube S2 of the K group half-bridge submodule that the second Modular multilevel converter MMC2 described in locking is to be charged, trigger the lower switching tube S2 conducting of the half-bridge submodule except K group of the second Modular multilevel converter MMC2, system is to the K group half-bridge submodule capacitor charging of the second Modular multilevel converter MMC2, when the second Modular multilevel converter MMC2 K group half-bridge submodule capacitor voltage reaches its set point, the K group charging of the second Modular multilevel converter MMC2 is complete, system proceeds to next the group half-bridge submodule capacitor charging to the second Modular multilevel converter MMC2,
Step 8: make K=K+1, if K is less than or equal to 4, then repeat step 7, otherwise, all half-bridge submodule electric capacity precharge of the lower switching tube S2 of locking second Modular multilevel converter MMC2 all half-bridges submodule, the second Modular multilevel converter MMC2 terminates.
Beneficial effect of the present invention:
(1) grouping precharge is adopted, no matter converter has a few phase, and also no matter brachium pontis contains how many half-bridge submodules, and the half-bridge submodule for the first Modular multilevel converter is only divided into two groups, four groups are only divided into for the second converter, substantially reduce the charging interval;
(2) the inventive method, on current-limiting resistance, voltage drop is much smaller than each only to voltage drop during single submodule charging, therefore greatly reduces the power of current-limiting resistance;
(3) do not need to detect charging current direction, control simple;
(4) do not need to drop into capacitance voltage closed-loop control, it is convenient to realize;
(5) half-bridge submodule control power supply can be got and can be powered by a capacitance voltage high position, does not need external control power supply.
Accompanying drawing explanation
Fig. 1 is Modular multilevel converter topological structure schematic diagram;
Fig. 1 a is the half-bridge submodular circuits schematic diagram of Fig. 1;
Fig. 2 a is the first Modular multilevel converter recharged capacitance grouping schematic diagram of the present invention;
Fig. 2 b is the second Modular multilevel converter recharged capacitance grouping schematic diagram of the present invention;
Fig. 3 is the electric capacity grouping pre-charge system wiring schematic diagram with a converter;
Fig. 4 is the electric capacity grouping pre-charge system wiring schematic diagram with two converters;
Fig. 5 is electric capacity of the present invention grouping precharge flow chart;
Fig. 6 is electric capacity of the present invention grouping pre-charge voltage curve chart.
Wherein, 1. the first Modular multilevel converter, 2. the second Modular multilevel converter, 3. half-bridge submodule, 4. circuit breaker RBK1,5. current-limiting resistance Rx, 6. AC power, 7. circuit breaker RBK2,8. Modular multilevel converter.
Embodiment
Below in conjunction with accompanying drawing and embodiment, the invention will be further described.
As shown in Figure 1, give two Modular multilevel converter topological structure schematic diagrames, it comprises the first Modular multilevel converter 1 and the second Modular multilevel converter 2, wherein, often have up/down two brachium pontis mutually, each brachium pontis is in series by N number of half-bridge submodule 3SM and reactor L; Fig. 1 a gives the topology diagram of half-bridge submodule 3, is with the power switch pipe (S1 and S2) of anti-paralleled diode and capacitor C to form by up/down two.S1 and S2 series connection is in parallel with capacitor C again.
Fig. 2 a gives the grouping schematic diagram of the first Modular multilevel converter 1MMC1 electric capacity precharge of the present invention, on first Modular multilevel converter 1MMC1, the upper half half-bridge submodule 3 of brachium pontis is 1 to the N/2 half-bridge submodule 3 often going up brachium pontis mutually, when N is even number, upper half is equal with bottom half half-bridge submodule 3 quantity, when N is odd number, each brachium pontis upper half and bottom half half-bridge submodule 3 number difference one, N/2 can adopt truncation or round up and carry out rounding process.Under first Modular multilevel converter 1MMC1, the group technology of brachium pontis is identical with the group technology of brachium pontis on above-mentioned first Modular multilevel converter 1MMC1, first Modular multilevel converter 1MMC 1 electric capacity precharge is divided into two groups, and two order of packets are any.The present embodiment adopts: using as the first Modular multilevel converter 1MMC1 electric capacity precharge first group of the upper half half-bridge submodule 3 of brachium pontis on the first Modular multilevel converter 1MMC1 and lower brachium pontis, and carry out precharge to first group simultaneously, using as the first Modular multilevel converter 1MMC1 electric capacity precharge second group of bottom half half-bridge submodule 3 electric capacity of brachium pontis on the first Modular multilevel converter 1MMC1 and lower brachium pontis, and carry out precharge to second group simultaneously.
Fig. 2 b gives the grouping schematic diagram of the second Modular multilevel converter 2MMC2 electric capacity precharge of the present invention, on second Modular multilevel converter 2MMC2, the upper half half-bridge submodule 3 of brachium pontis is 1 to N/2 the half-bridge submodule 3 often going up brachium pontis mutually, in second Modular multilevel converter 2, the bottom half submodule of brachium pontis is often go up the N/2+1 of brachium pontis mutually to N number of half-bridge submodule, when N is even number, upper half is equal with bottom half half-bridge submodule 3 quantity, when N is odd number, each brachium pontis upper half and bottom half half-bridge submodule 3 number difference one, N/2 can adopt truncation or round up and carry out rounding process.Under second Modular multilevel converter 2MMC2, the group technology of brachium pontis is identical with the group technology of brachium pontis on above-mentioned second Modular multilevel converter 2MMC2.Second Modular multilevel converter 2MMC2 electric capacity precharge is divided into four groups, and four order of packets are any.The present embodiment adopts: using as the second Modular multilevel converter 2MMC2 electric capacity precharge first group of the upper half half-bridge submodule 3 of brachium pontis on the second Modular multilevel converter 2MMC2, using as the second Modular multilevel converter 2MMC2 electric capacity precharge second group of the upper half half-bridge submodule 3 of brachium pontis under the second Modular multilevel converter 2MMC2, using as the second Modular multilevel converter 2MMC2 electric capacity precharge the 3rd group of the bottom half half-bridge submodule 3 of brachium pontis on the second Modular multilevel converter 2MMC2, using as the second Modular multilevel converter 2MMC2 electric capacity precharge the 4th group of the bottom half half-bridge submodule 3 of brachium pontis under the second Modular multilevel converter 2MMC2.
Fig. 3 gives the wiring schematic diagram of the electric capacity pre-charge system containing a Modular multilevel converter 8MMC, and in figure, Modular multilevel converter 8MMC AC is connected with AC power 6 by current-limiting resistance Rx5 and circuit breaker RBK14.
Fig. 4 gives the wiring schematic diagram of the electric capacity pre-charge system containing two ends Modular multilevel converter 8, in figure, the first Modular multilevel converter 1MMC1 AC is connected with AC power 6 by current-limiting resistance Rx5 and circuit breaker RBK14, second Modular multilevel converter 2MMC2 AC circuit breaker RBK27 disconnects all the time in electric capacity pre-charge process, and the first Modular multilevel converter 1MMC1 is connected by two DC buss with the second Modular multilevel converter 2MMC2.
It is Modular multilevel converter 8 electric capacity of the present invention grouping pre-charge method flow chart that Fig. 5 gives.Electric capacity precharge step for two Modular multilevel converter 8 of Fig. 4 is specifically implemented as follows:
(1) switching tube S1 and S2 of all half-bridge submodules 3 of locking, cut-off breaker BRK27, closed AC power 6 and circuit breaker BRK14, first system enters uncontrollable rectifier pre-charging stage;
(2) after capacitor charging makes all half-bridge submodule 3SM control power work normal, grouping pre-charging stage is proceeded to;
(3) the lower switching tube S2 conducting of second group of half-bridge submodule 3 of described first Modular multilevel converter 1MMC1 is triggered, system is to first of the first Modular multilevel converter 1MMC1 group of half-bridge submodule 3 capacitor charging, when the first Modular multilevel converter 1M,MC1 first group of half-bridge submodule 3 capacitance voltage reaches its set point, first group of charging terminates, the lower switching tube S2 of now locking first Modular multilevel converter 1M,MC1 second group of half-bridge submodule 3, trigger the lower switching tube S2 conducting of first group of half-bridge submodule 3 of converter first Modular multilevel converter 1MMC1, system is to second of the first Modular multilevel converter 1MMC1 group of half-bridge submodule 3 capacitor charging, when the first Modular multilevel converter 1 second group of half-bridge submodule 3 capacitance voltage reaches its set point, second group of charging terminates, the lower switching tube S2 of locking first Modular multilevel converter 1M,MC1 first group of half-bridge submodule 3, so far, all half-bridge submodule 3 electric capacity precharge of the first Modular multilevel converter 1MMC1 terminates,
(4) system proceeds to the grouping pre-charging stage of described second Modular multilevel converter 2MMC2, if the grouping of the second Modular multilevel converter 2MMC2 K represents (K=1,2,3,4), if the initial value of K is 1;
(5) the lower switching tube S2 of the K group half-bridge submodule 3 that locking second Modular multilevel converter 2MMC2 is to be charged, trigger the lower switching tube S2 conducting of the half-bridge submodule 3 except K group of the second Modular multilevel converter 2MMC2, system is to K group half-bridge submodule 3 capacitor charging of the second Modular multilevel converter 2MMC2, when the second Modular multilevel converter 2MMC2 K group half-bridge submodule 3 capacitance voltage reaches its set point, the charging of K group is complete, system proceeds to next group half-bridge submodule 3 capacitor charging to the second Modular multilevel converter 2MMC2,
(6) K=K+1 is made, if K is less than or equal to 4, then repeat step (5), otherwise, all half-bridge submodule 3 electric capacity precharge of lower switching tube S 2, the second Modular multilevel converter 2MMC2 of locking second Modular multilevel converter 2MMC2 all half-bridges submodule 3 terminates.
Charging order in above-mentioned steps (3) between each group of the first Modular multilevel converter 1MMC1 can exchange.
Charging order in above-mentioned steps (4) to (6) between each group of the second Modular multilevel converter 2MMC2 can exchange.
What provide for Fig. 3 only has a Modular multilevel converter 8MMC, then ignore (4) of above-mentioned steps to (6).
After all submodule electric capacity precharge of Modular multilevel converter terminates, before system normal operation input, need described current-limiting resistance 6Rx short circuit to fall.
Fig. 6 give be electric capacity of the present invention grouping pre-charge method charging voltage oscillogram.
By reference to the accompanying drawings the specific embodiment of the present invention is described although above-mentioned; but not limiting the scope of the invention; one of ordinary skill in the art should be understood that; on the basis of technical scheme of the present invention, those skilled in the art do not need to pay various amendment or distortion that creative work can make still within protection scope of the present invention.
Claims (4)
1., based on a grouping pre-charge method for the grouping pre-charge system of Modular multilevel converter electric capacity, it is characterized in that,
The grouping pre-charge system of Modular multilevel converter electric capacity comprises: at least one Modular multilevel converter MMC, the AC input of described Modular multilevel converter MMC is connected with AC successively and is started current-limiting resistance Rx, AC circuit breaker RBK1 is connected with AC power supply, described Modular multilevel converter comprises brachium pontis and lower brachium pontis in M phase, described brachium pontis comprises N number of half-bridge submodule SM, N number of half-bridge submodule SM series connection is connected with reactor L, described half-bridge submodule comprises power switch tube S 1 and lower power switch tube S 2, power switch tube S 1 and lower power switch tube S 2 are in parallel with electric capacity C after connecting,
The concrete steps of this grouping pre-charge method are:
Step one: to the half-bridge submodule grouping of respectively going up mutually in Modular multilevel converter MMC in brachium pontis and lower brachium pontis;
Step 2: switching tube S1 and S2 of all half-bridge submodules of locking, closed AC power and circuit breaker BRK1, enter uncontrollable rectifier pre-charging stage;
Step 3: after capacitor charging makes all half-bridge submodule SM switch controlled power works normal, proceed to grouping pre-charging stage;
Step 4: to the electric capacity grouping charging in the half-bridge submodule of Modular multilevel converter MMC;
A kind of concrete packet mode of described step is: in setting, first half-bridge submodule of brachium pontis and lower brachium pontis is first group to N/2 half-bridge submodule, N/2+1 half-bridge submodule to N number of half-bridge submodule in setting in brachium pontis and lower brachium pontis is second group, adopts the method rounded up to carry out rounding process when N is odd number;
Concrete steps in described step 4 are:
(1) the lower switching tube S2 conducting of second group of half-bridge submodule of described Modular multilevel converter MMC is triggered, system is to first of Modular multilevel converter MMC group of half-bridge submodule capacitor charging, when Modular multilevel converter MMC first group of half-bridge submodule capacitor voltage reaches its set point, first group of charging is complete;
(2) the lower switching tube S2 of lock modules multi-level converter MMC second group of half-bridge submodule, the lower switching tube S2 conducting of first group of half-bridge submodule of trigger mode blocking multi-level converter MMC, system is to second of Modular multilevel converter MMC group of half-bridge submodule capacitor charging, when Modular multilevel converter MMC second group of half-bridge submodule capacitor voltage reaches its set point, second group is also charged complete;
(3) all half-bridge submodule electric capacity precharge of lower switching tube S2, the Modular multilevel converter MMC of lock modules multi-level converter MMC first group of half-bridge submodule terminates.
2., based on a grouping pre-charge method for the grouping pre-charge system of Modular multilevel converter electric capacity, it is characterized in that,
The grouping pre-charge system of Modular multilevel converter electric capacity comprises: at least one Modular multilevel converter MMC, the AC input of described Modular multilevel converter MMC is connected with AC successively and is started current-limiting resistance Rx, AC circuit breaker RBK1 is connected with AC power supply, described Modular multilevel converter comprises brachium pontis and lower brachium pontis in M phase, described brachium pontis comprises N number of half-bridge submodule SM, N number of half-bridge submodule SM series connection is connected with reactor L, described half-bridge submodule comprises power switch tube S 1 and lower power switch tube S 2, power switch tube S 1 and lower power switch tube S 2 are in parallel with electric capacity C after connecting,
Described Modular multilevel converter comprises two Modular multilevel converter MMC, be respectively the first Modular multilevel converter MMC1 and the second Modular multilevel converter MMC2, described first Modular multilevel converter MMC1 and the second Modular multilevel converter MMC2 is linked together by DC bus, the AC input of the first Modular multilevel converter MMC1 starts current-limiting resistance Rx, circuit breaker RBK1 and AC power with series connection successively and is connected, and the AC output of the second Modular multilevel converter MMC2 is connected with circuit breaker RBK2;
The concrete steps of this grouping pre-charge method are:
Step one: to the half-bridge submodule grouping of respectively going up mutually in the first Modular multilevel converter MMC1 in brachium pontis and lower brachium pontis;
Step 2: to half-bridge submodule average packet all in the second Modular multilevel converter MMC2;
Step 3: switching tube S1 and S2 of all half-bridge submodules of locking, cut-off breaker BRK2, closed AC power and circuit breaker BRK1, first system enters uncontrollable rectifier pre-charging stage;
Step 4: after capacitor charging makes all half-bridge submodule SM switch controlled power works normal, proceed to grouping pre-charging stage;
Step 5: to the capacitor charging in the half-bridge submodule of the first Modular multilevel converter MMC1;
Step 6: system proceeds to the grouping pre-charging stage to the second converter MMC2, if the grouping of MMC2 represents with K, K=1,2,3,4, if the initial value of K is 1;
Step 7: to the capacitor charging in the half-bridge submodule of the second Modular multilevel converter MMC2;
Step 8: make K=K+1, if K is less than or equal to 4, then return step 7, carry out next group capacitor charging of MMC2, otherwise, all half-bridge submodule electric capacity precharge of the lower switching tube S2 of locking second Modular multilevel converter MMC2 all half-bridges submodule, the second Modular multilevel converter MMC2 terminates;
The concrete steps of described step 5 are:
(1) the lower switching tube S2 conducting of second group of half-bridge submodule of described first Modular multilevel converter MMC1 is triggered, system is to first of the first Modular multilevel converter MMC1 group of half-bridge submodule capacitor charging, when the first Modular multilevel converter MMC1 first group of half-bridge submodule capacitor voltage reaches its set point, first group of charging is complete;
(2) the lower switching tube S2 of locking first Modular multilevel converter MMC1 second group of submodule, trigger the lower switching tube S2 conducting of first group of half-bridge submodule of the first Modular multilevel converter MMC1, system is to second of the first Modular multilevel converter MMC1 group of half-bridge submodule capacitor charging, when the first Modular multilevel converter MMC1 second group of half-bridge submodule capacitor voltage reaches its set point, second group is also charged complete;
(3) the lower switching tube S2 of locking first Modular multilevel converter MMC1 first group of half-bridge submodule, so far, all half-bridge submodule electric capacity precharge of the first Modular multilevel converter MMC1 terminates;
The concrete steps of described step 7 are:
(1) the lower switching tube S2 of the K group half-bridge submodule that the second Modular multilevel converter MMC2 described in locking is to be charged, trigger the lower switching tube S2 conducting of the half-bridge submodule except K group of the second Modular multilevel converter MMC2, system is to the K group half-bridge submodule capacitor charging of the second Modular multilevel converter MMC2, when the second Modular multilevel converter MMC2 K group half-bridge submodule capacitor voltage reaches its set point, the charging of K group is complete;
(2) system proceeds to next the group half-bridge submodule capacitor charging to the second Modular multilevel converter MMC2.
3. the grouping pre-charge method of a kind of grouping pre-charge system based on Modular multilevel converter electric capacity as claimed in claim 2, it is characterized in that, the concrete packet mode of described step one is: in setting, first half-bridge submodule of brachium pontis and lower brachium pontis is first group to N/2 half-bridge submodule, N/2+1 half-bridge submodule to N number of half-bridge submodule in setting in brachium pontis and lower brachium pontis is second group, adopts the method rounded up to carry out rounding process when N is odd number.
4. the grouping pre-charge method of a kind of grouping pre-charge system based on Modular multilevel converter electric capacity as claimed in claim 2, it is characterized in that, concrete packet mode in described step 2 is: first the half-bridge submodule setting each phase of the second Modular multilevel converter MMC2 is first group to N/2 half-bridge submodule, setting the second Modular multilevel converter MMC2 respectively descends first of brachium pontis half-bridge submodule to be second group to N/2 half-bridge submodule mutually, N/2+1 half-bridge submodule to the N number of half-bridge submodule setting the upper brachium pontis of the second Modular multilevel converter MMC2 is the 3rd group, setting the second Modular multilevel converter MMC2 respectively descends N/2+1 half-bridge submodule to N number of half-bridge submodule of brachium pontis to be the 4th group mutually, adopt the method rounded up to carry out rounding process when N is odd number.
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